We spent the Cold War in perpetual fear that the U.S. and U.S.S.R. would start an intentional nuclear conflict. The truth is, we came far closer to blowing ourselves up with nuclear weapons than we ever came to WWIII.

Nuclear incidents have a bunch of ominous military code names, like Broken Arrow, Faded Giant or NUCFLASH. There are actually dozens of instances like these, but here are five major ones that happened in the U.S. If we were to consider Soviet activity, the list could go on for hours. The Russians either lost a nuclear sub, lost a sub with nuclear weapons on board, had a nuclear sub's reactor melt down, or all three roughly every other week. Kompetentnyh? Nyet.

Travis Air Force Base, 1950 — Broken Arrow

During the Korean War, U.S. military and political officials gave serious consideration to the use of atomic weapons. In August of 1950, ten B-29 Superfortress bombers took off from what was then called Fairfield-Suisun Air Force Base in California, headed for Guam. Each was carrying a Mark IV atom bomb, which was about twice as powerful as the bombs dropped on Japan at the end of World War II.

Shortly after takeoff, one of the B-29s had engine trouble. On board was General Robert Travis. He commanded the plane to turn back to the base when the landing gear refused to retract. Sensing the plane was going down, the pilot tried to avoid some base housing before crashing at the northwest corner of the base. The initial impact killed 12 of the 20 people aboard, including General Travis. The resulting fire eventually detonated the 5,000 pounds of conventional explosives that were part of the Mark IV. That massive explosion killed seven people on the ground. Had the bomb been armed with its fissile capsule, the immediate death toll may have reached six figures.

The Air Force covered up the incident, blaming it on conventional bombs loaded for a training flight. The base was renamed for General Travis just a few months later. The term Broken Arrow refers to nuclear incidents which are not likely to start a nuclear war.
Fermi 1 breeder reactor, 1966 — Faded Giant

What happened at Fermi 1 was the result of engineering mistakes, lax safety standards and simple inexperience at building nuclear reactors. The designers made changes to the cooling system without documenting them, so the engineers working on the reactor didn't know that there were extra dispersion plates in the liquid sodium containment tank. When one of the tanks blocked the coolant pipes, the reactor core overheated to 700 degrees F and partially melted down.

In a meltdown, the reactor fuel overheats beyond the point that the cooling system can handle. It eventually begins to melt the infrastructure surrounding it, such as containment casings, cooling systems and, in extreme cases, the floor of the installation. In a full meltdown, the fuel catches fire and sustains itself at about 2,000 degrees F. Although the term wasn't in use in 1966, the hypothetical (and technically impossible) chance of a burning reactor melting its way through the Earth all the way to China gives us the term "China Syndrome."

Fermi 1 actually sits in between Detroit and Toledo, but I guess "We Almost Lost Toledo" doesn't have quite the same ring to it. Faded Giant, by the way, is the codeword for a non-weapon nuclear incident like this (who actually goes around using these code words, I have no idea).
Tybee Island, 1958 — Broken Arrow

In the waters off Tybee Island, Georgia, right at the Georgia/South Carolina border and not far from Savannah, buried in about 10 feet of silt is a hydrogen bomb. It's been there for more than 50 years.

In 1958, a B-47 Stratojet bomber suffered a mid-air collision during training exercises. It was carrying a Mark 15 hydrogen bomb at the time – a lightweight bomb 12 feet long and carrying 400 pounds of explosives and highly enriched uranium. The damaged bomber's crew decided that this wasn't the sort of thing they wanted to be carrying when they attempted a crash landing, so they asked for and received permission to dump the bomb in the ocean. It did not explode when it hit the water, and was never seen again.

There is some discrepancy as to whether the bomb was fully armed. Some reports suggest it was, but the Air Force officially lists it as containing a dummy capsule. Several attempts have been made to locate it, but the natural radiation of the surrounding geology has made this difficult. If it had been armed, and had detonated, the city of Savannah would have pretty much disappeared.
Idaho Falls, 1961 — Faded Giant

You're probably expecting to find Three-Mile Island on this list. That was potentially a serious disaster, and it did release radioactive gas into a populated area. But the Idaho Falls incident stands out as the most gruesome U.S. nuclear disaster, and it's relatively little known.

The SL-1 reactor was an experimental reactor run by the U.S. Army near Idaho Falls, Idaho. On the night of January 3, 1961, heat alarms went off. Nearby emergency personnel made their way to the scene. They could not reach the control room for more than an hour and a half because of high radiation levels. When they did, they found two victims, one clinging to life (he died not long after). Even after being removed from the reactor building, the corpses themselves were so radioactive they had to be buried in lead and concrete tombs.

The worst was still to come. Several days later, rescue crews found the third operator. He had been standing atop the reactor when the incident occurred, and the force of the explosion had blasted a control rod up and through his chest, pinning him to the ceiling.

The key to the incident was the crew's ability to control the rate of the reaction. A sustainable reaction requires each fission event to generate enough neutrons to strike an additional atom, generating one more fission event. Control is maintained by manipulating the probability of a neutron causing fission, mainly through control rods of a material that harmlessly absorbs the neutrons. Putting more controls rods into the reactor slows the reaction. SL-1 was undergoing maintenance that required a few inches of the main control rod to be removed. Since this reactor design used one big control rod, a single mistake (withdrawing almost the entire control rod) caused the reaction to instantly go supercritical – fission events occurring and exponentially multiplying.

The massive jump in energy output vaporized the water coolant and parts of the reactor itself, resulting in a powerful explosion. The explosion itself caused the reaction to halt. I'm still waiting for Gil Scott-Heron to write "We Almost Lost Idaho Falls."

NORAD, 1979 — NUCFLASH (almost)

This is how NORAD learned not to run computer simulations of Soviet nuclear attacks on the systems used to respond to actual Soviet nuclear attacks. The missile defense agency received alarming indications that a full scale battery of Russian nukes were heading toward the U.S. Planes were scrambled with fully armed nuclear weapons. The president's shielded emergency plane was put into the air too (although they couldn't get the president on it in time).

Fingers hovered over buttons. Commanders of flight crews waited for word to strike. For six tense minutes, no one was sure if World War III was happening…and oddly, no one used the "red phone" hotline to ask the Soviets. Finally, word came from Advanced Early Warning radar and satellites that no missiles were detected. The culprit? A training tape had accidentally been run and generated the false positive signals. In military parlance, a NUCFLASH is an actual nuclear detonation that might lead to an outbreak of nuclear war.

An honorable mention goes to the Duluth bear, in which a guard saw a bear climbing a fence at an Air Force base and rang an alarm. The alarm connected to other nearby bases, but one of them was wired wrong, so instead of "intruder alert!" they got the "Nuke Russia Now!" alarm. Nuclear armed jets were on the runways ready to take off before the mistake was rectified.

If that doesn't seem scary enough, there are dozens more incidents like these on the U.S. side alone. We haven't even touched on the Cuban Missile Crisis. The sad lesson is that we have less to fear from naked aggression than we do from incompetence and bad engineering.